Many vehicles now include a tire pressure monitoring system (TPMS) that monitors the air pressure in the tires of the vehicle and reports the tire pressure and/or an under-inflation condition to the driver. While different TPMS designs exist, it is most common for a TPMS to employ an internal or valve stem mounted sensor-transmitter (sensor) on each wheel, which sensor communicates tire pressure readings to a vehicle mounted receiver. Radio frequency (RF) transmission is typically the means by which the TPMS sensors communicate with the receiver.
Because the sensors transmit RF signals to the receiver, the sensors are typically battery powered. Further, because it is obviously desirable to conserve battery life, a TPMS sensor is normally not energized until after a wheel into which the sensor has been installed is mounted to a vehicle. In the case of new vehicles, a TPMS sensor initialization process is commonly employed at some point during vehicle manufacture.
Known TPMS sensor initialization processes typically use one or, more commonly, a plurality of stationary antennas that are located along the path of an assembly area through which associated vehicles pass. As a vehicle passes the stationary antenna(s), the TPMS sensors are automatically activated, their data is read, and the data is subsequently written to the vehicle's engine control unit (ECU) or another vehicle-located control device. The use of a plurality of antennas arranged along the path of the vehicle is common in order to provide ample time to activate the sensors on all four wheels of a vehicle as it moves past the antennas. Antenna manufacturers require that the antennas remain stationary during the sensor initialization process to prevent any problems with RF communication between the antennas and the TPMS sensors.
Alternatively, TPMS sensor initialization may be accomplished with a hand-held wand that is independently placed in close proximity to each wheel of a vehicle. Although this method eliminates the need for multiple activation antennas, it requires a human user to walk around a vehicle and properly locate the wand to each wheel for an adequate time. Thus, while the number of activation antennas may be reduced, the time to perform the initialization process and the associated manpower is generally increased by this method.
Once the TPMS sensors of a vehicle have been activated, their data must be read and provided to a control unit in the vehicle. Commonly, TPMS sensor data is written to the vehicle's ECU. Thus, the assembly line area at which TPMS sensor initialization is performed is frequently also equipped with a remote receiver for receiving and recording data from the TPMS sensors of each vehicle, and a transmitter for transmitting the TPMS sensor data to the ECU or other controller located in the corresponding vehicle. In addition to requiring extra time to perform this portion of the TPMS initialization process and additional space for the central receiver(s), line-side remote transmission of TPMS sensor data to a vehicle's ECU may be problematic due to interference from other nearby TPMS initialization systems or other equipment in the area. Because of this, TPMS sensor initialization may occur off-line or in special assembly areas in some vehicle manufacturing facilities. Alternatively, a reduced line speed and special precautions and/or methods may be utilized to ensure proper sensor initialization and data transmission.
In light of the issues with known TPMS initialization systems and methods, it would be desirable to provide a system and method of activating vehicle TPMS sensors that reduces the time, space and number of antennas required to accomplish sensor initialization. It would also be desirable to reduce or eliminate problems associated with the transmission of TPMS sensor date to a vehicle ECU or other receiver.